EDITORIAL NOTE AT THE SPECIAL ISSUE: NEA/CSNI/WGAMA specialists meeting on nuclear thermal-hydraulics in water cooled reactors

International audienceA Specialists Meeting on Transient Nuclear Thermal-Hydraulics (NTH) in water cooled reactors (SM-TH) was organized by the OECD Nuclear Energy Agency (NEA) Committee on the Safety of Nuclear Installations (CSNI) Working Group on the Analysis and Management of Accidents (WGAMA) together with the Consejo de Seguridad Nuclear (CSN). Initially, it was intended to be hosted by CIEMAT in Madrid (Spain) in December 2020, but was finally held virtually in March 2022 due to the COVID-19 (NEA/CSNI/R (2023)1). The key goal of the SM-TH was to summarize the current status in NTH and to formulate recommendations to CSNI for activities in the area.The meeting gathered nearly 70 experts from industry, safety authorities, research institutes and universities in 16 countries to discuss the achievements and the needs of safety research in nuclear reactor accident thermal-hydraulics. About 70 papers have been presented at the meeting, discussing the state of the art and maturity of NTH for evaluating safety of existing reactors, identifying strengths and drawbacks of the current analysis approaches, and defining the needs and priorities of research on safety-related NTH, particularly under accident conditions.This special issue is a collection of the selected papers that summarizes the key outcomes of the SM-TH, after a careful peer reviewer process